as3894.3

AS 3894.320021

Australian StandardTM

Site testing of protective coatings

Method 3: Determination of dry film thickness

PREFACE

This Standard was prepared by the Australian members of the Joint StandardsAustralia/Standards New Zealand Committee CH-003, Paints and Related Materials, tosupersede AS/NZS 3894.3:1993. After consultation with stakeholders in both countries,Standards Australia and Standards New Zealand decided to develop this Standard as anAustralian Standard rather than an Australian/New Zealand Standard.

The terms normative and informative have been used in this Standard to define theapplication of the appendix to which they apply. A normative appendix is an integral partof a Standard, whereas an informative appendix is only for information and guidance.

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CONTENTS

Page

FOREWORD ................................................................................................................... 3

SECTION 1 SCOPE AND GENERAL1.1 SCOPE......................................................................................................................... 41.2 REFERENCED DOCUMENTS................................................................................... 41.3 DEFINITIONS............................................................................................................. 41.4 TEST METHODS........................................................................................................ 51.5 PRECAUTIONS .......................................................................................................... 51.6 INSPECTION PERIOD ............................................................................................... 61.7 INSPECTION PLANS................................................................................................. 61.8 INSPECTION OBJECTIVES .................................................................................... 10

SECTION 2 MAGNETIC INSTRUMENT METHODMETHOD A2.1 SCOPE....................................................................................................................... 112.2 PRINCIPLE ............................................................................................................... 112.3 APPARATUS ............................................................................................................ 112.4 PREPARATION OF TEST SURFACE ..................................................................... 112.5 PRECAUTIONS ........................................................................................................ 122.6 PROCEDURE............................................................................................................ 122.7 REPORT.................................................................................................................... 13

SECTION 3 MAGNETIC INDUCTION AND EDDY CURRENT METHODSMETHOD B3.1 SCOPE....................................................................................................................... 133.2 APPLICATION ......................................................................................................... 133.3 PRINCIPLE ............................................................................................................... 143.4 APPARATUS ............................................................................................................ 143.5 PREPARATION OF TEST SURFACE ..................................................................... 143.6 PRECAUTIONS ........................................................................................................ 143.7 PROCEDURE............................................................................................................ 153.8 REPORT.................................................................................................................... 16

APPENDICESA MICROGRAPHIC EXAMINATION OF CROSS-SECTIONS ................................. 17B MICROSCOPIC MEASUREMENT OF PAINT FLAKES ........................................ 20C WET FILM THICKNESS BY COMB GAUGE ........................................................ 22D CALIBRATION OF MEASURING INSTRUMENTS .............................................. 27E A SAMPLE REPORT FORM FOR DRY FILM THICKNESS TESTING ................ 30

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FOREWORDWhen determining a method of measuring the dry film thickness of a protective coating inthe field, the following factors need to be taken into account:

(a) The need for an uncoated reference substrate that has a surface preparation identicalto that of the work piece.

(b) Provision of standard test blocks bearing a calibrated non-magnetic coating that istraceable to a national Standard, i.e. NBS or DIN.

(c) The utilization of non-magnetic or non-metallic shims.

(d) Calibration of instruments and adjustment of instruments.

(e) Examination of coating on various faces as a sampling process.

(f) Expression of results.

The protective coating system examined here is not a separately manufactured article butone that is part of a manufactured product. There are several ways in which the concept ofthickness, or its quantitative expression, differs from those criteria that usually characterizethe thickness of sheets, foils, films, plates and tubes.

The durability of the protective coating system can be governed by the thickness of film,above the asperities of the substrate that is lying outside the peaks of the surface profile.Measurement of this film thickness at a large number of arbitrarily chosen spots on the testpiece will commonly yield a number of readings, some of which are 50% greater thanothers. At the same time, on any face of the test piece, a mean value for a large number ofreadings will differ from the mean value of the reading observed on another face. It is theobjective of this Standard to achieve uniformity of practice in dealing with such adistribution of film thickness values.

The coating surface in view may be sensibly smooth even though it has a waviness on thelarge scale. As well as being hidden and inaccessible to the instrument, the underside of theprotective film replicates the irregularity of the surface profile, on both the small and thelarge scale.

Many of the methods available for examining the dry film thickness of a paint coating on atest panel are not for the use of site testing of protective coatings because of the inability toweigh the work piece, measure volume of coatings, or to mar the coating by destructivetesting. It is for this reason that only non-destructive instruments, operating on magnetic orelectromagnetic principles, have any practical use. The range of thicknesses of protectivecoatings is usually beneath the level of discrimination of acoustic instruments.

ISO 2808, and Steel Structures Painting Council Specification SSPC-PA-2 provideadditional information on the determination of film thickness.

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METHOD1 SCOPE

This Standard provides practical test methods for the on-site determination of the range ofthicknesses and the mean dry film thickness of a protective coating system, or itscomponent coats, upon a metallic structure or fabrication.

The coated fabrications to which the methods may be applied include tanks or reservoirs,bridge girders, equipment used in processing chemicals or petroleum, pipelines, andfabricated articles such as vehicles, white goods and other items of industrial production,where there is lack of uniformity of substrate thickness, metallographic character, surfacecondition and the film of the protective coating.

NOTES: 1 Appendix A provides a laboratory test method for the microscopic determination of the

thickness of the film adhering to a substrate. This method would only be used where no othermethod is acceptable.

2 Appendix B provides a method for determining the thickness of a flake of the coating usingan optical microscope.

3 ISO 2808 provides information on additional methods of determining film thickness.

2 REFERENCED DOCUMENTS

The following documents are referred to in this Standard:AS1199 Sampling procedures and tables for inspection by attributes1399 Guide to AS 1199Sampling procedures and tables for inspection by

attributes2483 Testing of coatingsAS/NZS1580 Paints and related materialsMethods of test1580.108.2 Method 108.2: Dry film thicknessPaint inspection gauge2310 Glossary of paint and painting terms2312 Guide to the protection of iron and steel against exterior atmospheric

corrosionISO2808 Paints and varnishes Determination of film thickness

3 DEFINITIONS

For the purpose of this Standard, the definitions of AS/NZS 2310 and those below apply:

3.1 Dry film thickness

The thickness of the coating measured, at any location on the test surface, above the peaksof the profile (anchor pattern or surface profile) of the substrate.

3.2 Primary standards

Reference standards that are maintained and housed under controlled conditions at theprincipal office of the test organization.

3.3 Reference substrate

A surface used to set the instrument zero, and for comparing results obtained from the testpiece.

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3.4 Secondary standards

Standards that are referenced to the primary standards and are used in the field.

4 TEST METHODS

The coating film thickness may be measured using magnetic pull-off gauges (see clause 9),or by eddy current or magnetic induction type instruments (see clause 10) of the typegenerally described in Table 1:

NOTES: 1 Owing to the inherent inaccuracies of some magnetic pull-off gauges, they are recommended

only for process control operations, where accurate and reproducible measurements are notrequired.

2 Appendix C provides a method for determining the wet film thickness during application of acoating, which will assist applicators in achieving the required dry film thickness.

5 PRECAUTIONS

The accuracy of measurement of a coating thickness may be affected by a number offactors. The following precautions should be observed:

(a) Calibration The instrument should be calibrated in accordance with Appendix Dprior to use, re-calibrated after each hour and rechecked at the end of the work period.

(b) Substrate thickness For each instrument, there is a critical thickness of metalsubstrate below which the accuracy of the instrument cannot be assured. Since thisthickness depends on both the measuring frequency of the probe system and theelectrical conductivity or the magnetic permeability of the substrate, its value shouldbe determined experimentally, unless it is specified by the manufacturer of the testinstrument.

(c) Edge effects Measurements should not be taken close to an edge, hole or insidecorner of a test specimen unless the instrument is calibrated for such measurements.

(d) Curvature Measurements are affected by the curvature of the specimen. Theinfluence of curvature varies considerably, depending on the make and type ofinstrument, but always becomes more pronounced as the radius of curvaturedecreases. Measurements made on curved test specimens will therefore not be validunless the instrument is specifically calibrated for such measurements.

(e) Surface profile and roughness Measurements are influenced by the surfacetopography of the substrate and of the coating. Rough surfaces and the anchor patternof a surface profile can cause both systematic and random errors.

(f) Foreign particles The probes of the coating thickness gauge need to make contactwith the test surface. The instruments are therefore sensitive to any foreign materialthat prevents intimate contact between the probe and surface of the coating. Theprobe tip should be checked periodically for cleanliness and foreign particlesremoved using plasticine or similar material.

(g) Soft coatings Soft coatings may be deformed by the probe. Valid measurements onsuch test specimens may only be possible with the use of special probes or fixtures.NOTE: When softness of the film is caused by the degree of cure, it may be necessary todefer testing.

(h) Surface contamination Sticky, greasy, tacky material, or other types ofcontaminants, may cause a build-up on the probe, so care should be taken that suchmaterial does not affect measurements.NOTE: If contamination is severe, it may become necessary to defer the testing.

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(i) Probe pressures Excessive pressure on the probe may damage a coating. Careshould be taken to ensure that magnetic instrument probes are held vertically and thatthe coating is not damaged by the probe when determining measurements.

(j) Electromagnetic fields Instruments may not operate correctly in the presence ofstrong electromagnetic fields. Inaccurate results may be obtained where strong fieldsare present, e.g. near aluminium smelter pot lines or in the vicinity of electric weldingactivities.

(k) Magnetic properties of pigments The magnetic effect of certain pigments andextenders, such as micaceous iron oxide (MIO) and red iron oxide, can affect theaccuracy of measurements obtained from some instruments.NOTE: Such errors are usually within the normal accuracy of the instrument and may not besignificant.

(l) Temperature effects Extremes of temperature may influence both the readingsobtained from the instrument and the deformation properties of the coating beingmeasured.

6 INSPECTION PERIOD

All thickness testing on the coating shall be performed at an appropriate time

(a) after the coating manufacturers specified handling time has elapsed, or when thecoating has hardened sufficiently so that it is not deformed by the application of theprobe;

(b) before the maximum permissible recoating period has elapsed; and

(c) not more than seven days after the manufacturers specified handling time haselapsed.

7 INSPECTION PLANS

7.1 General

When devising an inspection plan for the number of measurements required to determinethe thickness of a coated finish, it is necessary to consider such aspects as

(a) the extent and duration of the project;

(b) when the inspection work is to be carried out;

(c) the configuration of the coated work, including the presence of braces, supports andother appurtenances; and

(d) the pattern of inspection points that has proved acceptable for previous projects thathave used the same coatings, the same methods of application, and operatives ofequivalent skill.

Clauses 7.3 to 7.5 provide a guide to inspection plans that have been found appropriate fordifferent programs of work. As each of Clauses 7.3 to 7.5 offers a different inspection plan,a procedure appropriate to the specific program of work needs to be selected.

7.2 Point reading

When determining a reading at a point on the coating, a single reading is sufficient.However, for suspect or disputed readings the mean of three separate gauge readings, takenwithin the area of a 12 mm diameter, should be recorded.

7.3 Large surface areas

For large areas of flat or uniformly curved coated surfaces, five separate point readings (seeClause 1.7.2), evenly spaced throughout, should be made in each 10 m2 area examined. The10 m2 inspection areas should be selected as follows:Ac

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(a) Structures not exceeding 30 m2 Each 10 m2 area should be measured.

(b) Structures not exceeding 100 m2 Three 10 m2 areas should be chosen at random andmeasured.

(c) Structures exceeding 100 m2 The first 100 m2 area should be measured in accordancewith Option (b), and for each additional 100 m2 area, a 10 m2 area should be chosen atrandom and measured.

(d) Where the thickness for any 10 m2 area chosen in accordance with Option (b) or (c)does not meet the required specification, then each 10 m2 area of surface should bemeasured.

NOTE: This inspection plan is recommended by the National Association of Corrosion Engineers(NACE) and Steel Structures Painting Council Specification SSPC-PA-2.

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TABLE 1

TYPICAL PROPERTIES OF FILM THICKNESS INSTRUMENTS

InstrumentNo.

TypeTest range

Typicalinstrumentaccuracy

Application Scale Calibration Remarks

1 Pencil gauge

Magneticpull-off

0600 m 15% Magneticsubstrates

Fixed Nil Inherentlyvariable in itsaccuracy

Suitable formid-rangereadings onlyon horizontalsurfaces

2 Banana gauge

Magnetictorsion pull-off models

010 000 musingseparatemodels

10% Magneticsubstrates

Fixed Singlepoint

Suitable foruse in anyorientationlocations

Hand-held,portable, ofmoderate costand suitablefor processcontrol

3 Multi-reelreadout

Magneticinduction

Electro-mechanicaloperation

02000 m 5 m*or5%

Magnetic ornon-ferroussubstrates,according tomodel

Fixed Singlepoint

Solid stateelectronicinstrumentsuitable forallapplicationsandorientations

Small,compact,battery-operated,hand-held

4 Magneticinduction

Electronicoperation

Analogueread out

02500 m 5 m*or5%

Magnetic ornon-ferroussubstrates,according tomodel

Adjustable Two points Solid stateelectronicinstrumentsuitable forallapplicationsandorientations

Small,compact,battery-operated,hand-held

5 Magneticinduction

Electronic-digital liquidcrystaldisplay(LCD)

020 000 m 2 m*or1%up to12 500 m5% greaterthan12 500m

Magneticsubstratesonly

Adjustable Two points Suitable forallapplicationsand roughsurfaces

Microprocessor control

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InstrumentNo.

TypeTest range

Typicalinstrumentaccuracy

Application Scale Calibration Remarks

(continued)

6 Magneticinduction andeddy current

Micro-processorcomputercontrolledLCD

010 000 m 2 m*or1% up to12 500 m5% greaterthan12 500 m

Magnetic ornon-ferroussubstrates

Adjustable Two points Microprocessor control forallapplications

Statistical/memorycapacity/batch analysis

Hard copyfacility

7 Paintinspectiongauge (PIG)

Cutter andopticalmicroscope

01.3 mm 10% All substrates Certificatefor cutter

Hand-operatedopticalmicroscope. Adestructivetest (refer toAS1580.108.2)

8 Opticalmicroscopewithmagnificationup to 500

2 m Measurementof film flake

RefereemethodNot suitablefor site use

* Whichever is the greater.

NOTE: Ultrasonic gauges are available to measure coating thickness on concrete, masonry, timber, glassand ceramics.

TABLE 2

SAMPLE INSPECTION PLAN FOR COATING

Number of 10 m2 areasin a batch

(Batch size)

Number of 10 m2

areas to berandomly selected

for test

(Sample size)

Maximum numberof defective 10 m2

areas for batch to beaccepted

(Acceptance number)

2 to 8 9 to 1516 to 25

235

000

26 to 5051 to 90

91 to 150

81320

001

151 to 280281 to 500

501 to 1 200

325080

123

1 201 to 3 200 3 201 to 10 00010 001 and over

125200315

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TABLE 1 (continued)

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7.4 Small surface areas

For small items and coating areas, point thickness measurements may be taken as follows:

(a) Flat areas less than 10 m2 A minimum of 3 point readings per square metre.

(b) Pipe work At each metre of pipe run, point readings shall be taken evenly around thecircumference as follows:

Nominal pipesize, mm

Number ofcircumferential

readings 150>150 300>300 600

246

(c) Beams/angles One reading on each flat face less than 300 mm in width, for eachlinear metre.

7.5 Statistical sampling

Depending on the nature of the work, it may be appropriate to devise a specific inspectionplan based on statistical sampling. Such a procedure will only be effective if the followingrequirements are met:

(a) The sample is drawn randomly from work of known history. The sample shouldenable verification of coatings produced at essentially the same time using essentiallythe same process and system of control.

(b) For each situation, a suitable inspection plan needs to be defined. An inspection plandevised for one contractor of given capability, when applying a particular coating,may not be relevant to another contractor applying the same coating.

For statistical sampling to be of value, the contractor needs to have a demonstratedlevel of expertise. Sampling and the establishment of an inspection plan should becarried out in accordance with AS 1199, guidance to which is given in AS 1399.

NOTE: Table 2 provides an example of an inspection plan based on an AQL of 1.5%.

8 INSPECTION OBJECTIVES

8.1 General

The procedures of Clause 9 or Clause 10 shall be followed, according to the type ofinstrument employed, to record an appropriate number of determinations with a properlycalibrated instrument.

The objective is to ascertain whether the structure or steel fabrication has the desiredthickness of protective coating; however, this is commonly a contractual matter between atleast two parties. For any point at which a measurement reveals a reading that is outside thespecification limits, it is not only necessary to inspect closely the immediate area toestablish the extent of the out-of-specification film, but also to identify and mark it forfurther consideration or action.

The criteria for further action will depend upon the service to which the substrate is likelyto be exposed, and are given in Clauses 1.8.2 to 1.8.4. In some instances, it may be essentialthat the specified maximum coating thickness be not exceeded, to ensure adequateperformance of the coating.

8.2 Severe environment

For surfaces that are to be immersed, buried or subjected to a very severe chemical ormarine environment, a minimum film thickness should be specified and achieved.

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Although, for cost-effective reasons, a specification may in such cases accept an absoluteminimum area of somewhat lower thickness, irrespective of the inspection plan adopted,any point thickness determination found to be outside the specified thickness range shouldbe identified to enable restorative action to be taken.

8.3 Atmospheric exposure

For structures exposed to the atmosphere, especially when protected by coating systemsnominated in AS/NZS 2312, the following requirements should be met:

(a) The average of five point readings for each 10 m2 area of coating surface should notbe outside the specified coating thickness range.

(b) No single point reading in any 10 m2 area should be less than 80% of the specifiedminimum coating thickness. However, where three readings are averaged to produce apoint reading, an individual reading may be less than 80% of the minimum coatingthickness.

8.4 Large numbers of small components

Where a statistical inspection plan is adopted, such as shown in Table 2, the number ofdefective areas should not exceed that permitted by the plan.

9 MAGNETIC INSTRUMENT METHODMETHOD A

9.1 Scope

These Clauses set out a method for measuring the thickness of non-magnetic dried coatings(Method A) on structural steel or other ferromagnetic substrates. It is intended for use withpaints that produce films that are firm and are not indented by the instruments used.

9.2 Principle

Instruments using the magnetic pull-off principle measure the force required to overcomethe attraction between a magnet and the magnetic substrate. The magnitude of the force isdependent on the distance between the magnet and the substrate, which, in the case ofpainted specimens, is the coating thickness.

9.3 Apparatus

9.3.1 Calibration standards

Standard test blocks bearing calibrated non-magnetic coatings that are traceable to asuitable national standard, covering the appropriate range of film thickness to be measured.

9.3.2 Magnetic pull-off instrument

Measuring the attractive force between the substrate and the magnet, which is separated bythe coating thickness to be measured.

The instrument may be one of a type incorporating either of the following:

(a) A spring that is extended by the action of lifting the instrument (by hand) with themagnet in place on the coating. The graduated extension at the point where themagnet leaves the coating provides a measure of film thickness.

(b) A counterbalance lever attached to the magnet and connected to a spiral torsionspring. The spring is wound up by smooth rotary action applied by the thumb, toincrease the force of retraction on the magnet lever. At the point of pull-off, thecalibrated dial provides a reading of film thickness.

NOTE: Instruments used in Option (a) are not recommended for routine inspection work.

9.4 Preparation of test surface

The test surface shall be clean, free of foreign matter and, if necessary, degreased using asuitable degreasing agent that does not attack the coating.A

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9.5 Precautions

9.5.1 General

In addition to factors referred to in Clause 1.5, magnetic pull-off instruments should besubject to the considerations given in Clauses 9.5.2 to 9.5.5.

9.5.2 Reproducibility

To ensure reproducibility of results, hand operation of the instrument should be carried outslowly with a smooth action.

9.5.3 Vibration

Care should be taken that vibration of the test surface does not influence the readingobtained.

9.5.4 Measuring

For instruments in Clause 9.3.2(b), the measuring uncertainty inherent in the method istypically 10% of the coating thickness. The inaccuracy is greater at each end of the scale.

9.5.5 Probe position

Care should be taken to ensure that the probes are held vertical to the test coating.

9.6 Procedure

The coating thickness shall be measured as follows:

(a) Select an instrument with a mid-range appropriate to the thickness to be measured.

(b) Ensure that the coating is firm and resists deformation prior to use of the instrument.

(c) Inspect the probe tip and the surface to be measured to ensure that they are clean.

(d) Calibrate the instrument in accordance with Appendix D.

(e) Take readings in areas that are free of vibration and electrical or magnetic fields.

(f) For a film thickness less than three times the profile height, measure the uncoatedsubstrate (A) at a number of points to obtain a representative average value, thenfollow Steps (g) and (h).

(g) Measure the dry coating film (B) at the specified number of points to obtain arepresentative average value.

(h) Subtract reading (A) from (B) to obtain the thickness of the coating film.NOTES: 1 When a fixed scale gauge is used, it is necessary to correct the A and B measurements

using the corrections determined in Steps (b) and (d) of Paragraph D5.2 Appendix A.2 Where the thickness of the measured coating exceeds three times the surface profile

height of the uncoated substrate, it is not necessary to determine a reading on uncoatedsubstrate for subtraction from the reading obtained over the coating.

3 For practical purposes, when the profile height is not accessible, as a guide a value of onethird of the expected profile height may be used as a correction for profile effects as adeduction from measurement B.

(i) If thickness readings are found outside the range of accuracy determined in Step (d),repeat the calibration procedure in that range. Check the calibration frequently duringuse to ensure that the instrument continues to read correctly.

(j) Recalibrate the instrument at appropriate periods (see Clause 1.5.1).

(k) Take a sufficient number of readings in accordance with Clause 1.7.

(l) Take measurements no closer than 25 mm to an edge, and no closer than 75 mm toanother mass of metal.

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NOTE: If measurements are required within these specified limits, recheck the calibration inthe specific area to determine the effect that the edge or mass of metal has on the instrumentreading.

(m) Record the results.

9.7 Report

The report shall include the following information:

(a) Name of testing organization/inspector.

(b) Date of the test and report number.

(c) Identification and description of the item tested and its coating, including shape,substrate material, coating type and specified film thickness.

(d) A description of the location where the test was conducted, the project identificationand the test conditions.

(e) Description of the test equipment used and calibration details.

(f) Film thickness measurements, in micrometres.

(g) Reference to this Australian/New Zealand Standard, i.e. AS/NZS 3894.3, Method A.

(h) Any deviations from this test method.NOTE: Appendix E provides a sample test report form.

10 MAGNETIC INDUCTION AND EDDY CURRENT METHODSMETHOD B

10.1 Scope

This Clause sets out methods for non-destructive measurement of the thickness of curedcoatings, as follows:

(a) Magnetic induction (low frequency) method For non-magnetic metallic coating andorganic coatings on magnetic substrates.

(b) Eddy current (high frequency) method For non-conductive coatings on non-magneticmetallic substrates.

(c) Eddy current (high frequency) method For metallic and non-metallic coatings onmetallic substrates which differ appreciably in conductivity.

10.2 Application

The methods may be applied to coatings and substrates referred to in Clause 3.1, where thecoating thickness is not less than 2 m, and the surface contour permits calibration of theappropriate instruments (see also Appendix D).

The magnetic induction (low frequency) method is suitable for the measurement ofnon-magnetic metallic coatings, such as silver, tin and zinc, and organic coatings such aspaints and plastics on magnetic substrates.

The eddy current (high frequency) method is frequently applied to the measurement oforganic coatings on non-magnetic metallic substrates and to the measurement of anodizedcoatings.

With suitable instruments using appropriate frequencies, it is possible to measure thethickness of various metallic coatings on either magnetic or non-magnetic substrates; e.g.tin-lead on copper, silver on nickel-silver, copper on steel, zinc on steel, cadmium on steel,tin on steel, copper on a non-metallic base, and silver on a non-metallic base.

These methods, under the best conditions of use, are accurate to 2 m, or 5%, whichever isthe greater.

NOTE: The methods are not suitable for the measurement of chemical conversion coatings.Acce

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10.3 Principle

An electromagnetic field is generated in the probe system of both the magnetic inductioninstrument and the eddy current instrument.

Magnetic induction instruments generate a low-frequency alternating current (typically50 Hz to 60 Hz) in a probe, which produces measurable magnetic induction when it isplaced on a test specimen with a magnetic metal substrate. A controlled oscillator producesa low-level alternating voltage, which energizes one coil in a multi-coil probe. This in turninduces a voltage in the coil in close proximity to the first. As the magnitude of this voltagedepends on the distance between the probe and the ferromagnetic substrate, this voltagerepresents the coating thickness.

Eddy current instruments generate higher frequencies in the probe (typically about6000 kHz), which produces eddy currents in the test specimen when the probe is placed onthe test surface. A single coil probe is driven by a low-level alternating voltage produced bya crystal controlled oscillator. This voltage induces small currents (eddy currents) whichflow in conductive materials in opposition to the original field and effectively reduce thevoltage across the coil. The change in voltage is dependent upon the distance of the probefrom a conductive substrate; this distance is the coating thickness.

10.4 Apparatus

An instrument that complies with the appropriate principle that is outlined in Clause 3.3 andwhich can be calibrated for the known thicknesses of coating (see Appendix D) is required.

10.5 Preparation of test surface

The test surface shall be clean, free of foreign matter and, if necessary, shall be degreasedusing a suitable degreasing agent that does not attack the coating.

10.6 Precautions

In addition to the factors in Clause 1.5, eddy current and magnetic induction typeinstruments should be subject to the following considerations:

(a) Conductivity of the substrate Measurements using eddy current instruments can beaffected by the electrical conductivity of the substrate. This is a function of thecomposition and heat treatment of the material. The influence of electricalconductivity on the measurement varies considerably with the make and type ofinstrument.

If the substrate alloy or its heat treatment changes, the zero reading should berechecked and the instrument recalibrated if necessary.

For eddy current instruments, the assumption is made that the full properties areknown. In the event that a change in substrate conductivity is suspected, a small areaof coating shall be removed to allow calibration of the instrument on the bare metal.

A rapid change in a series of readings may indicate that there is a change in substratecomposition.

(b) Measuring accuracy The measuring uncertainty inherent in this method is typically2 m or 5% of the coating thickness, whichever is the greater.

(c) Probe temperature The characteristics of the probe may vary as the temperaturechanges. Wherever possible, measurement should only be taken under the conditionsthat apply during calibration of the instrument probe combination. Where extremesurface temperatures are encountered, the probe manufacturers advice should besought.

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10.7 Procedure

The coating thickness shall be measured as follows, using the method appropriate to thecoating (see Clause 3.2):

(a) Check that the substrate thickness is greater than the critical minimum thicknessspecified by the instrument manufacturer.

(b) Ensure that the coating is firm and resists deformation prior to use of the instrument.

(c) Inspect the probe tip and the surface to be measured to ensure that they are clean.

(d) Check the calibration of the instrument on a smooth substrate similar to that beingtested (see Appendix D).

(e) Press the probe on the point to be measured, at right angles to the test surface.

(f) For a film thickness less than three times the profile height, measure the uncoatedsubstrate (A) at a number of points to obtain a representative average value, thenfollow Steps (g) and (h).

(g) Measure the dry coating film (B) at the specified number of points to obtain arepresentative average value.

(h) Subtract reading (A) from (B) to obtain the thickness of the coating film.NOTES: 1 When a fixed scale gauge is used, it is necessary to correct the A and B measurements

using the corrections determined in Steps (b) and (d) of Paragraph D5.2, Appendix D.2 Where the thickness of the measured coating exceeds three times the surface profile

height of the uncoated substrate, it is not necessary to determine a reading on theuncoated substrate for subtraction from the reading obtained over the coating.

3 For practical purposes, when the profile height is not accessible, as a guide a value of onethird of the expected profile height may be used as a correction for profile effects as adeduction from measurement B.

(i) Recalibrate the instrument at appropriate periods (see Clause 1.5.1).

(j) Take a sufficient number of readings in accordance with Clause 1.7.

(k) Record the results.NOTE: Appendix E shows a typical form that may be used to record results.

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10.8 Report

The report shall include the following information:

(a) Name of testing organization/inspector.

(b) Date of the test and report number.

(c) Identification and description of the item tested and its coating, including shape,substrate material, coating type and specified film thickness.

(d) A description of the location where the test was conducted, the project identificationand the test conditions.

(e) Description of the test equipment used and calibration details.

(f) Film thickness measurements, in micrometres.

(g) Reference to this Australian/New Zealand Standard, i.e. AS/NZS 3894.3, Method B.

(h) Any deviations from this test method.NOTE: Appendix E provides a sample test report form.

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APPENDIX A

MICROGRAPHIC EXAMINATION OF CROSS-SECTIONS

(Informative)

A1 SCOPE

This Appendix sets out the method for measuring the local thickness of protective coatingsby micrographic examination of cross-sections.

The method is suitable for measuring the thickness of protective coatings on varioussubstrates. It provides a general method for measuring, to within 2 m or better, thethickness of a protective coating on a section cut from a test panel or coated article.

It is recommended as a referee method where a dispute cannot be resolved concerning thethickness of a protective coating. It is particularly useful for measuring variations inthickness, which occur due to unevenness of the substrate, for example on grit-blasted steel.

A2 PRINCIPLE

Test specimens are cut from coated products, prepared for testing and then examinedmicrographically.

A3 APPARATUS

A microscope fitted with distance measuring equipment such that the uncertainty is notgreater than 2 m.

A4 PREPARATION OF TEST SPECIMENS

A4.1 General

Test specimens should be free of foreign matter and, if necessary, should be degreased in asolvent that does not attack the coating.

For soft coatings, with thickness less than 50 m, the degreased surface of the coatingshould be painted with a contrasting plastics coating. The paint should not be reactive withthe coating to be measured.

A4.2 Mounting of test specimen (see Note 1)

The test specimen may be mounted in a plastics material that is neither reactive to noraffects the coating, e.g. a suitable clear-coating cold-setting resin or material such as Plasterof Paris. Care should be taken to ensure that voids do not form between the test specimenand the mounting material, and that the coated surface is at right angles to the surface beingground and polished (see Note 2).

NOTES: 1 When testing coated sheet and strip metals, test specimens may be appropriately clamped

prior to mounting and polishing.2 A deviation of only 10 from the vertical introduces an error of approximately 2% in the

coating thickness determination.

A4.3 Grinding and polishing

The surface of the test specimen, prepared as described in Paragraph A4.1, is generally in acondition suitable for the grinding operation. Should burrs be present on either the testpiece or its mountings, they may be removed by means of a smooth file.

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The test specimen is to be ground and polished in accordance with good micrographicpractice. The following procedure has been found to be satisfactory:

(a) Abrade the test specimen with successively finer silicon carbide wet and dry abrasivepapers placed on a flat glass plate and copiously lubricated with water during thegrinding process.NOTE: A satisfactory finish is generally obtained by first using P180 grade paper and thensuccessively using P360, P600 and P1200 grades.

(b) In each case, immediately before passing to the next finer grade of paper, the testspecimen should be abraded with a back and forth movement in a straight line toensure that, before washing, scratches due to that particular paper are in onedirection.

(c) On transferring the test specimen to the next finer paper, rotate the test piece through90% and then repeat the back and forth movement across previous scratches untilthey disappear. This provides a convenient way of determining when to transfer thetest specimen to the next finer grade of paper.

(d) When operations have been finished on the finest grade paper, rinse and polish thetest specimen by using either a water suspension of a suitable polishing medium, suchas finely divided magnesium oxide, aluminium oxide, or diamond dust (0 to 1 m)suspended in a suitable wax or paste. The polishing operation should be carried outusing a soft cloth without the use of undue pressure.NOTES: 1 Selvyt cloth or chamois, or materials of similar softness, are suitable polishing cloths.2 The following precautions will facilitate the preparation of satisfactory test specimens:

(a) Polished surfaces should not be fingered.(b) Polishing pads should be covered when not in use to avoid contamination by

airborne dust.(c) At the completion of the polishing process, the surface should be washed with a

suitable solvent, rinsed in alcohol and dried in an air stream.

A5 PROCEDURE

The coating thickness is measured as follows:

(a) Project the image of the test specimen section onto the screen of a metallographicmicroscope at a known and properly calibrated magnification.

(b) Measure accurately the thickness of the deposit on the projected image using agraduated linear scale.

The actual thickness of the coating may be determined by dividing this measurementby the magnification, or by measuring the thickness using a metallurgical microscopefitted with a micrometer eyepiece that has been calibrated against an accuratelygraduated reference scale.

In either case the magnification used should be sufficient to allow the thickness of thecoating to be determined to the required accuracy.

(c) A minimum of 10 readings should be made. The thickness of the coating should beread from the highest peak of the metal substrate in the field of view.

(d) Record the result in micrometres.

A6 REPORT

The report should include the following information:

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(b) Relevant product specification.

(c) Each thickness measurement of the coating, in micrometres.

(d) Report number and date.

(e) Reference to this test method, i.e. AS/NZS 3894.3, Appendix A.

(f) Any deviations from this test method.

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APPENDIX B

MICROSCOPIC MEASUREMENT OF PAINT FLAKES

(Informative)

B1 SCOPE

This Appendix sets out a method of speedily determining the film thickness of smallspecimens of paint flakes removed from the substrate, using a micrographic examination ofthe cross-sections. The method also allows the determination of the number and thicknessof visibly different overlapping coatings.

B2 PRINCIPLE

A cross-section of a paint flake is mounted in wax or plasticine on a glass slide and isexamined and its thickness is measured under a microscope.

B3 APPARATUS

B3.1 Optical microscope

Binocular type of variable magnification up to 100, fitted with appropriate measuringgraticules.

B3.2 Camera

Where required, capable of being used in conjunction with the microscope (B3.1).

B4 PREPARATION OF THE TEST SPECIMEN

The specimen is prepared as follows:

(a) Snap the flake to be examined or, in the case of a very flexible specimen, tear theflake to present as straight an edge as possible. Do not cut or polish the specimen asthis will blur the detail and burr the edges.

(b) Mount the specimen in wax or plasticine, on a glass slide.

(c) Ensure that the specimen is held vertically and edge-onto the lens.NOTE: A deviation of only 10 from the vertical introduces an error of approximately 2% inthe coating thickness determination.

(d) Adjust the flake to expose as large a portion of the edge as possible, positioned atright angles to the lens mounting.

B5 PROCEDURE

The test procedure is as follows:

(a) Illuminate and focus on the cross-sectional edge, using the lowest magnification first,e.g., 50.NOTE: For measurement of film thickness, 50 and 100 are the most frequently usedmagnifications.

(b) Align the linear graticule across the flake and record the measurement.

(c) Determine the thickness of the specimen by viewing through the microscope. Thereadings on the graticule are interpreted as follows:

(i) 50 1 mm on the graticule represents 2000 m.

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(ii) 100 1 mm on the graticule represents 1000 m.(d) Determine the thickness of the specimen by producing a micrograph. The specimen

thickness may be measured from the print using the following conversion:

(i) 50 1 mm represents 20 m.(ii) 100 1 mm represents 10 m.

(e) Record the measured thickness of the specimen.

B6 REPORT

The report should include the following information:

(a) Test specimen identification.

(b) Relevant product specification.

(c) Each thickness measurement of the coating, in micrometres.

(d) Report number and date.

(e) Reference to this test method, i.e. AS/NZS 3894.3, Appendix B.

(f) Any deviations from this test method.

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APPENDIX C

WET FILM THICKNESS BY COMB GAUGE

(Informative)

C1 SCOPE

This Appendix describes a method of determining a field measurement of the wet filmthickness of a coating using a comb gauge.

The comb gauge gives only a rough indication of wet film thickness and consequently isused mainly for field checks during painting operations and to show that major deviationsin film thickness are not occurring. Use of a suitable correction factor with the wet filmthickness obtained by the comb gauge will provide an estimate of the dry film thickness ofthe finished coating.

C2 PRINCIPLE

The comb gauge is inserted in the wet film, normal to the coated surface, and is thenexamined to determine the shortest tooth touching the coating.

C3 APPARATUS COMB GAUGE

Of metal or plastics material, the outer teeth of which form a baseline (see Figure C1). Theinner teeth are progressively shorter, thus presenting a range of gaps between the tips of theteeth and the baseline which correspond to a scale marking on the gauge.

C4 PROCEDURE

The procedure is as follows:

(a) Immediately after the application of the paint, place the comb gauge firmly onto thesubstrate in such a way that the teeth are normal to the plane of the surface.

(b) Remove the gauge and examine the teeth to determine which is the shortest one tohave touched the wet paint film.

(c) Record the film thickness as lying between the last touching tooth and firstnon-touching tooth, as shown on the tooth calibrations marked on the gauge.

(d) Take at least two further readings in different places to obtain representative resultsover the painted area.

(e) Clean the gauge teeth after each film thickness determination.

(f) If required, estimate the dry film thickness using a conversion method given inParagraph C5.

C5 ESTIMATION OF DRY FILM THICKNESS

The dry film thickness may be estimated from a wet film measurement using the followingequation:

tvWFT = DFT

+

100 . . . C5(1)

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where

DFT = dry film thickness, in micrometres

WFT = wet film thickness, in micrometres

v = volume solids in paint before thinning, as a percentage

t = thinner added to paint, as a percentage

The required wet film thickness to achieve a desired dry film thickness may be estimatedfrom the following equation:

vt)+(DFT=WFT 100 . . . C5(2)

Alternatively, Table C1 may be used to determine the percentage volume solids present,after thinning the paint. Table C2 or Figure C2 may be used to determine the wet filmthickness required to achieve a specified dry film thickness for thinned paint containing ofvarying percentages volume solids.

C6 REPORT

Where a test report is required, it should contain the following information:

(a) The name of the project.

(b) The identification of the product tested.

(c) The date of the test.

(d) The average wet film thickness measured.

(e) If required, the estimated dry film thickness obtained after applying a statedcorrection factor.

(f) Reference to this test method, i.e. AS/NZS 3894.3, Appendix C.

(g) Any deviations from this test method.

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TABLE C1

REDUCED PERCENTAGE VOLUME SOLIDS IN PAINT AFTER THINNING

Percentage of thinner addedPercentagevolume solids

before thinning 2 3 5 6 7 10 12 18 25 37

100 98 97 96-95 94 93 91 89 84 80 73

95 93 93 91-90 90 89-88 87 85 81 77 70

90 88 87 86 84 84 82 80 76 72 66

85 83 82 81 80 79 78 76 72 68 62

80 78 78 77-76 75 74 73 71 68 64 58

75 73 73 72 71 70 69-68 67 63 60 55

70 68 68 67 66 65 64 62 59 56 51

65 64 63 62 61 60 60-59 58 55 52 47

60 59 58 57 57 55-56 55 53 51 48 44

55 54 53 53-52 52 51 50 49 46 44 40

50 49 48 48 47 46 46 45 42 40 36

45 44 44 43 42 42 41 40 38 36 33

40 39 39 38 38 37 37-36 36 34 32 29

35 34 34 34 33 33 32 31 30 28 28

30 29 29 29 28 28 27 27 25 24 22

25 24 24 24 24 23 23 22 21 20 18

TABLE C2

WET FILM THICKNESS, IN MICROMETRES, TO ACHIEVE SPECIFIED DRYFILM THICKNESS FOR PAINT OF VARIOUS VOLUME SOLIDS

Percentage volume solids in applied filmRequireddry film

thicknessm

35 40 45 50 55 60 65 70 75 80 85 90 95

25 71 63 56 50 46 42 39 36 33 31 29 28 26

50 143 125 111 100 91 83 77 71 67 63 59 56 53

75 214 188 167 150 136 125 115 107 100 94 88 83 79

100 286 250 222 200 182 167 154 143 133 125 118 111 105

125 357 313 278 250 227 208 192 179 167 156 147 139 132

150 429 375 333 300 273 250 231 214 200 188 176 167 158

175 500 438 389 350 318 292 269 250 233 219 206 194 184

200 571 500 444 400 364 333 308 286 267 250 235 222 211

250 714 625 556 500 455 417 385 357 333 313 294 278 263

300 857 750 667 600 546 500 462 429 400 375 353 333 316

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DIMENSIONS IN MILLIMETRES

FIGURE C1 TYPICAL COMB GAUGE

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APPENDIX D

CALIBRATION OF MEASURING INSTRUMENTS

(Normative)

D1 SCOPE

This Appendix provides requirements for and information on the calibration of magneticpull-off gauges and magnetic induction and eddy current measuring instruments.

D2 GENERAL

Instruments shall be operated in accordance with the manufacturers instructions. Usingsuitable thickness standards, calibration shall be carried out in the range of thicknesses tobe measured during the tests.

To ensure consistency of measurements, recalibration checks using secondary standards orsuitable reference substrates shall be carried out at frequent intervals during testing.

The type of calibration standards used will depend on the type of instrument and the natureof the coating under test.

D3 CALIBRATION STANDARDS

D3.1 General

Primary standards for magnetic pull-off gauges and magnetic induction and eddy currentmeasuring instruments shall be in accordance with Paragraph D3.2. Secondary standardsmay be in accordance with Paragraph D3.3.

D3.2 Primary standards

Primary standards shall be test blocks bearing calibrated non-magnetic coatings that aretraceable to a national standard. They may consist of small panels, each uniform inthickness, covering the appropriate range of film thicknesses to be measured.

NOTE: Eddy current measuring instruments may only be calibrated using a non-metallic coatingon a metal substrate, or a substrate with a coating having the same magnetic properties as thematerial under test.

D3.3 Secondary standards

Secondary standards may take the form of plastic films, shims or precoated referencepanels, made either of plastics materials or a non-magnetic metal, which give a similarequipment response to the coating to be tested, e.g. shims of non-magnetic metal such asbrass for the magnetic pull-off gauge, and plastics for the other types of instruments.

The use of plastic films is advantageous for the calibration of instruments used formeasuring curved surfaces.

To avoid errors in measurement, ensure intimate contact between a film and the substrate.

Calibration foils are subject to indentation and require replacement when worn or damaged.Resilient foils should not be used.

D4 REFERENCE SUBSTRATES

Substrate references are used for setting the zero and comparing results obtained from thetest piece. Reference substrates may be made from the material under test or may be anuncoated smooth metal plate. The reference substrate should be of similar geometry forsmall or curved sections. For use with magnetic induction instruments, they may also beA

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made from material having similar permeability as the material under test. For eddy currentinstruments, material having similar electrical response properties may be used.

The reference substrate should be smooth, without roughness or profile.

When the substrate thickness is below the minimum critical thickness, the thickness may bebuilt up by adding packing pieces of the same metal. However, packing pieces should onlybe used as a last resort.

Packing pieces are not suitable when the substrate is coated on both sides or when there is agap between the substrate and the back-up metal.

D5 PROCEDURE

D5.1 General

The calibration of test equipment entails simulating the coating under test by use ofincremental thicknesses of calibration foils, films or coating standards.

Instruments shall be adjusted during calibration, in accordance with the manufacturersinstructions (see Paragraphs D5.2 and D5.3). Appropriate calibration standards shall beused.

Magnetic pull-off gauges shall be calibrated in accordance with Paragraph D5.2. Magneticinduction instruments and eddy current instruments shall be calibrated in accordance withParagraph D5.3.

D5.2 Magnetic pull-off gauges

Instruments that are capable of calibration shall be calibrated using the followingprocedure:

(a) Measure the thickness on a primary standard (see Paragraph D3.2), at or slightlyabove the expected range of coating thickness.

(b) Depending upon the type of instrument, either adjust the reading or record thecalibration variation at standard thickness. To guard against gauge drift during use,recheck the gauge with one or more of the standards at least once each hour and oncompletion of each work shift.

(c) Record the thickness of the calibration standards.

(d) Crosscheck in the field using a precoated reference panel as a secondary standard, ator slightly above the expected range of coating thickness.NOTE: Although not ideal, for practical purposes in the field, shims may be used as asecondary standard as an alternative to precoated reference panels.

(e) When the gauge adjustment has drifted so far that large corrections are needed,readjust closer to the standard values and recalibrate. When the gauge can no longerbe adjusted to the calibration standards, have it rebuilt or replaced.

(f) Do not zero the gauge on the profile of the uncoated substrate.

D5.3 Magnetic induction and eddy current instruments

The procedure for calibration is as follows:

(a) Adjust the zero of the instrument on the smooth clean reference substrate (seeParagraph D4).

(b) Hold the instrument probe firmly against a primary or secondary standard, but avoidexcessive pressure, which could indent the coating.

(c) Set the instrument while holding the probe firmly against the calibration film.

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(d) Confirm the instrument setting by measuring the calibration film at several areas ofthe smooth clean reference substrate.

(e) Recheck the instrument using Steps (a) through to (d) as needed to obtain an averagesetting representative of the calibration range.

(f) Record the thickness of the calibration standard.

(g) Recheck the instrument setting at hourly intervals to guard against gauge drift duringuse.

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APPENDIX E

A SAMPLE REPORT FORM FOR DRY FILM THICKNESS TESTING*

(Informative)

TEST REPORT AS 3894.3 METHOD A/B

Site testing of protective coatingsDry film thickness

Project: .............................................................................................................................

Contract No.: ....................................................................................................................

Name of testing laboratory/authority: .............................................................................

Date of conduct of test: .................................Report number: ...........................................

Identification/description of test item

Substrate material: ............................................................................................................

Surface profile: ..................................................................................................................

Description of workpiece: ..................................................................................................

Coating system: ................................................................................................................

Method of coating application and date: .............................................................................

Curing conditions (time/temperature): ................................................................................

Method of cure: .................................................................................................................

Specified dry film thicknessMaximum: .......................... Minimum: .............................

Test procedure

Make and model of instrument used: .................................................................................

Calibration standard thickness: ..........................................................................................

Test results (attach results sheets)

Dry film thickness: (micrometres)

Maximum ......................................................... Minimum ..........................................

Readings taken .................................................... Total No: .........................................

No. above specification ............................... No. below specification ..............................

Inspectors name (print) ...................................... Signature .........................................

Name of contractor's representative (print): ...................................................................

Signature of contractor's representative: .......................................................................

Average dry film thicknessconforms to specified thickness

Yes No

* Modification of this form may be necessary depending on the size and scope of the project.

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This Australian Standard was prepared by Committee CH-003, Paints and Related Materials. It was approved on behalf of theCouncil of Standards Australia on 29 March 2002 and published on 7 June 2002.

The following are represented on Committee CH-003:

Australian Paint Approval SchemeAustralian Paint Manufacturers FederationAUSTROADSBuilding Research Association of New ZealandInstitution of Professional Engineers New ZealandMaster Painters AustraliaNational Association of Testing Authorities AustraliaNew Zealand Abrasive Blasting AssociationNew Zealand Manufacturers FederationNew Zealand Painting Contractors AssociationSurface Coatings Associatoin AustraliaTelstra CorporationWater Corporation Western Australia

Additional interests participating in the preparation of this Standard:

Australian Institute of Protective CoatingsBlast Cleaning and Coating Association QldSydney Water Corporation

Keeping Standards up-to-dateStandards are living documents which reflect progress in science, technology and systems. To maintain their currency, all Standards areperiodically reviewed, and new editions are published. Between editions, amendments may be issued. Standards may also be withdrawn. Itis important that readers assure themselves they are using a current Standard, which should include any amendments which may have beenpublished since the Standard was purchased.Detailed information about Standards can be found visiting the Standards Australia web site at www.standards.com.au and looking up therelevant Standard in the on-line catalogue.Alternatively, the printed Catalogue provides information current at 1 January each year, and the monthly magazine, The AustralianStandard, has a full listing of revisions and amendments published each month.We also welcome suggestions for the improvement in our Standards, and especially encourage readers to notify us immediately of anyapparent inaccuracies or ambiguities. Contact us via email at [email protected], or write to the Chief Executive, Standards AustraliaInternational Ltd, GPO Box 5420, Sydney, NSW 2001.

Originated as AS 3894.31993.Second edition 2002.

This Standard was issued in draft form for comment as DR 01387.

COPYRIGHT Standards Australia International

All rights are reserved. No part of this work may be reproduced or copied in any form or by any means, electronicor mechanical, including photocopying, without the written permission of the publisher.

Published by Standards Australia International LtdGPO Box 5420, Sydney, NSW 2001, Australia

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AS 3894.3-2002 SITE TESTING OF PROTECTIVE COATINGS - DETERMINATION OF DRY FILM THICKNESSPREFACECONTENTSFOREWORDMETHOD1 SCOPE2 REFERENCED DOCUMENTS3 DEFINITIONS3.1 Dry film thickness3.2 Primary standards3.3 Reference substrate3.4 Secondary standards

4 TEST METHODS5 PRECAUTIONS6 INSPECTION PERIOD7 INSPECTION PLANS7.1 General7.2 Point reading7.3 Large surface areas7.4 Small surface areas7.5 Statistical sampling

8 INSPECTION OBJECTIVES8.1 General8.2 Severe environment8.3 Atmospheric exposure8.4 Large numbers of small components

9 MAGNETIC INSTRUMENT METHOD-METHOD A9.1 Scope9.2 Principle9.3 Apparatus9.3.1 Calibration standards9.3.2 Magnetic pull-off instrument

9.4 Preparation of test surface9.5 Precautions9.5.1 General9.5.2 Reproducibility9.5.3 Vibration9.5.4 Measuring9.5.5 Probe position

9.6 Procedure9.7 Report

10 MAGNETIC INDUCTION AND EDDY CURRENT METHODS-METHOD B10.1 Scope10.2 Application10.3 Principle10.4 Apparatus10.5 Preparation of test surface10.6 Precautions10.7 Procedure10.8 Report

APPENDIX A - MICROGRAPHIC EXAMINATION OF CROSS-SECTIONSA1 SCOPEA2 PRINCIPLEA3 APPARATUSA4 PREPARATION OF TEST SPECIMENSA4.1 GeneralA4.2 Mounting of test specimen (see Note 1)A4.3 Grinding and polishing

A5 PROCEDUREA6 REPORT

APPENDIX B - MICROSCOPIC MEASUREMENT OF PAINT FLAKESB1 SCOPEB2 PRINCIPLEB3 APPARATUSB3.1 Optical microscopeB3.2 Camera

B4 PREPARATION OF THE TEST SPECIMENB5 PROCEDUREB6 REPORT

APPENDIX C - WET FILM THICKNESS BY COMB GAUGEC1 SCOPEC2 PRINCIPLEC3 APPARATUS - COMB GAUGEC4 PROCEDUREC5 ESTIMATION OF DRY FILM THICKNESSC6 REPORT

APPENDIX D - CALIBRATION OF MEASURING INSTRUMENTSD1 SCOPED2 GENERALD3 CALIBRATION STANDARDSD3.1 GeneralD3.2 Primary standardsD3.3 Secondary standards

D4 REFERENCE SUBSTRATESD5 PROCEDURED5.1 GeneralD5.2 Magnetic pull-off gaugesD5.3 Magnetic induction and eddy current instruments

APPENDIX E - A SAMPLE REPORT FORM FOR DRY FILM THICKNESS TESTING*

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